Leaf stripping is a technique that consists in eliminating a more or less sizeable quantity of leaves located in the fructiferous zone of plants. Done manually for a long time in some vineyards, this operation, which aims to improve the quality of the harvest and to make easier the manual work of thinning and picking, is experiencing a growing interest with the development of mechanical leaf stripping.
The interests in leaf stripping are manifold:                Promote the aeration of bunches of grapes in order to reduce rot;        Promote thinning in order to improve the coloration (thicker grape skin);        Thin out the vegetation layer in the fructiferous zone for better penetration and localization of treatments (botrytis; oidium; gray mold; grape worm; mildew)        Improve the maturation of the grapes by a better exposure to the sun (grapes heavier, flavors more developed and a better sanitary state of the grape harvest);        Promote access to the grapes in order to reduce the time of labor in manual operations such as thinning (−50%), manual harvesting (−30% to −40%);        Reduce the foliage in order to limit the losses of juice due to the intake of leaves from the rest of the harvest when it is done mechanically; and        Make drying easier in case of rain by a better exposure to the sun and a better aeration.        
Leaf stripping thus turns out to be an operation that is very much of interest and that corresponds well to the problem of optimization of tasks and the pursuit of quality of the harvest.
Several machines and processes have been proposed to date and some of them are currently still being used to accomplish this work.
According to a technique for leaf stripping developed by the applicant, in order to accomplish the task, a machine is used that consists of an open rotary drum, an intake mechanism that makes it possible to generate an intake flow of air that passes from the drum through the lateral cylindrical wall having lateral openings, a mechanism to direct the flow of air through a varying portion of the lateral wall, in a manner so as to catch and pin the leaves against the open lateral wall of the rotary drum, and a system for leaf stripping that makes it possible to pick off the leaves pinned against this wall.
For example, in the document FR-2,417,932-A, a device for leaf stripping is described that uses an open rotary cylindrical cage to roll on the vegetation layer and inside of it, a hollow cylinder is housed affixed and equipped with an opening. An aspirator mounted above the inside hollow cylinder makes it possible to create, inside of the inside cylinder, a partial vacuum that has the effect of sucking in the leaves of the vegetation and pinning them against the open rotary cage facing the opening of the fixed cylinder. Contact rollers mounted on articulated supports are applied under pressure against the lateral surface of the cage and are driven in rotation by this surface. The leaves come to get caught between the turning open drum and the contact rollers, and are torn off of the branches under the force of traction resulting from the movement of the machine.
A priori, the principle of parting of the foliage by means of an intake flow of a turbine through an open rotary drum that makes it possible to pull and pin the leaves on the lateral surface of the drum appears clever and economical. It does not appear, however, that the machine described in the document FR-2,417,932 was put on the market, and to the knowledge of the applicant, no stripping machine using this principle is being marketed today.
The failure of this machine results certainly from the fact that the principle of separating the leaves using frictional contact rollers does not appear to be able to be applied concretely for several reasons.
Following the description and the drawings of document FR-2,417,932, the articulated supports mounted on springs carrying the contact rollers are assigned to be arranged, during work, in the vegetation layer; this arrangement can not be applied due to the fact that these supports rub in the vegetation layer and hinder the aspiration of the leaves because they push back the vegetation; it is not possible to arrange the mechanical instruments in the vegetation layer beyond the wall of the rotary cage, since they would collide with and be torn off by various obstacles located in the axis of the vine row, such as stakes, guy wires, and above all, poles.
Due to the fact that a relatively sizeable force is necessary in order to remove the leaves by tearing them off, it is hardly probable that the force generated by friction of the contact rollers on the drum will be sufficient, especially if the leaves or the vine shoots become positioned between the wall of the cage and the contact rollers.
This device, as a result of its position relative to the vegetation layer, and as a result of its principle of separating the leaves by tearing them off, can only cause jamming of the system by accumulation of the plants and damage to the vine.
According to the document FR-2,808,964 A, the applicant has proposed a leaf stripping machine more specifically designed for stripping the leaves of a vine, consisting of at least one leaf stripping head, consisting of an open rotary drum, an aspiration mechanism making it possible to create an intake air flow going through the lateral cylindrical opened wall of this drum, a mechanism to channel this air flow through a varying portion of the lateral wall, and a cutting mechanism installed near the portion of the lateral wall of the turning intake drum oriented in parallel or approximately parallel to its axis of rotation, the cutting mechanism is arranged behind a diametral plane of the rotating drum oriented perpendicularly to the direction of movement of the machine during work.
This machine represents a first stage of progress to the extent that it makes it possible to perform leaf stripping with a quality comparable to a trimming of the vegetation layer, taking into account the fact that the leaves are cut and not torn, contrary to the solutions previously proposed which remove the leaves by tearing them off using blades or knives, or jamming contact rollers.
After separating, the leaves remain pinned against the opened lateral wall of the turning drum and are driven outside the intake field by the rotation of this wall. When the portion of the lateral wall covered with cut leaves is isolated from the intake field by the channeling baffle of the intake flow, the leaves, no longer subjected to the attraction of the air flow, fall due to gravity. This result comprises another advantage, because it eliminates projections of torn leaves likely to cause risks of disease as a result of the particles and dust propelled by blast of the turbine onto the adjacent vine rows.
However, it has been noted that the quantity of the leaves removed remained insufficient to obtain all of the sought-after results, the partial vacuum generated by the aspirator mechanism does not always exert a strong enough traction action to move the leaves that are only pinned against the turning drum, in the direction of the cutting mechanism.
The document WO 01/87047 A describes an evolution of the leaf stripping machine shown in the document FR-2,808,964 A.
According to this document, the leaf stripping head or each leaf stripping head of the leaf stripping machine consists of a tracked guide mechanism comprised of an endless opened belt wound, on the one hand, on the turning aspirating drum and, on the other hand, on a second drum arranged in front of the aspirating drum, the endless opened belt having, on the side of the leaf stripping machine assigned to face the vegetation layer, comprised of the vine row, during work, a trajectory or rectilinear portion, parallel to the path of movement of the leaf stripping machine, in a manner so as to have a planar support surface.
The opened tracked mechanism created in this way has the function of ensuring a good guidance and stability of the leaf stripping head on the vegetation layer. It ensures a flexible support of the leaf stripping head on the vegetation layer, while avoiding crushing the vegetation layer as a result of its large contact surface.
On the other hand, the cutting mechanism of the machine described in the document WO-01/87047 is comprised of a spiral cutting bar consisting of, on the one hand, a cutting screw comprised of a cylindrical rotary shaft equipped with a spiral threading having at least one sharp edge and, on the other hand, a bed knife comprised of a fixed cylindrical sleeve, open laterally, and inside of which the cutting screw is housed.
It has been observed that the machine constructed in this way tears the leaves to pieces and tears off a non-negligible quantity of young vine shoots.
In summary, though the two versions of the leaf stripping machines described, respectively, in the document FR-2,808,964 A, and in the document WO 01/87047 A have made it possible to simplify the technical nature of utilization of the equipment, while improving the quality of the leaf stripping machine, it has been noted:                that the adjustment of the intensity of the leaf stripping is still difficult and depends on the dexterity of the driver of the machine;        that the percentage of leaves cut to pieces or lacerated is not always negligible; and        that the quantity of injuries inflicted on the grape bunches, especially when the leaf stripping is done late in the season, still remains an unresolved problem for the wine-growers.        
The invention notably has the objective of proposing solutions to the problems mentioned above.